Location services based on the location of mobile devices are becoming increasingly widespread. Assistance data for assisted navigation systems, such as global navigation satellite systems (GNSS), e.g. Global Positioning System (GPS), GLObal NAvigation Satellite System (GLONASS) and Galileo, have been specified and standardized for cellular systems. For instance, the delivery of such assistance data can be built on top of cellular system-specific control plane protocols including, e.g., the radio resource location services protocol (RRLP) for GSM networks, the radio resource control (RRC) layer of layer 3 in wideband code division multiple access (WCDMA) networks, IS-801 for CDMA networks and LTE Positioning Protocol LPP for E-UTRAN, standardized in 3GPP/3GPP2.
The Open Mobile Alliance (OMA) has defined a user plane protocol referred to as secure user plane location (SUPL). SUPL employs user plane data bearers for transferring location assistance information such as GNSS assistance data, as described above, for carrying positioning technology-related protocols between terminal, e.g., a mobile communication device and its operating network. SUPL is intended to be an alternative and, at the same time, a complement to the existing standards based on signaling in the mobile network control plane. SUPL assumes that a mobile or other network can establish a data bearer connection between a terminal and some type of location server. The use of a user plane protocol becomes especially appealing incase of IP networks where the data bearer is available by nature.
The assistance data delivery from the assistance data server to the terminal is normally initiated by an assistance data request originating from the terminal or positioning request originating from the server. As a response, the assistance data is delivered to the terminal. This is typical request-response type signaling which does not require any memory from the server as the request is served immediately.
Another way of delivering assistance data is to broadcast it. In this case, the same data is delivered to the group of terminals. For example, in a cellular network all terminals camped to one base station will receive the same information. This data can be, however, encrypted and decryption keys need to be requested separately to limit the user group. Still, when transmitting the assistance data, the server does not need to know which terminal belongs to the user group that receives the information or that can decrypt the information.